contrib/init: add DARKFI_LOG to darkwiki initd

contrib/init/wikid.initd

@@ -19,7 +19,7 @@ start() {
 			--user $USER \
 			--env HOME="${PWHOME:-/home/$USER}" \
 			--name darkwikid \
-			--exec /usr/bin/screen -- -D -m -S darkwikid /usr/local/bin/darkwikid
+			--exec DARKFI_LOG=/home/$USER/wiki.log /usr/bin/screen -- -D -m -S darkwikid /usr/local/bin/darkwikid
 	eend $?
 }